1. Field of Invention
The present invention relates to a magneto-optical recording medium which performs data writing, erasing and rewriting using rays of light, and to a method of manufacturing the medium. More particularly, the invention relates to an improvement of environmental resistance by strengthening the close adhesion of the protective film to the photosetting resin through plasma etching after it is formed, to strengthen the environmental resistance of a metal film.
2. Description of the Prior Art
In a conventional magneto-optical recording medium, a vertical magnetizing film is usually formed on the recording layer by using an amorphous metallic material, such as Tb-Fe, Tb-Fe-Co, Gd-Fe-Co or Gd-Co.
However, as the recording layer contains a rare-earth metallic element, such as Tb or Gd, it is easily oxidized by moisture or oxygen in the air, such that the Kerr angle of rotation, the Faraday angle of rotation, magnetic resistance, transmissivity or reflexibility undergoes a great change, and angular formation of the Kerr hysteresis loop and faraday hysteresis loop characteristics become relatively poor. Consequently, the recording layer is unable to keep the properties of photomagnetism on a stabilized basis, and is thereby impractical for use as a medium which will keep data for many hours.
It is a generally known method to add an element, such as Pt, Ti, Cr, or Al, to the substance on the recording layer or to form a protective film by continuous sputtering or vacuum evaporation of a nitride, a sulphide or an oxide, such as Si.sub.3 N.sub.4, AlN, ZnS, or SiO.sub.2, on the recording layer in the vacuum tank in order to solve such a problem as described above.
When the above method is put to practical use, a drop in environmental resistance or oxidization resistance is shown. Consequently, photosetting resin which is not pervious to air and moisture is applied to the protective layer.